Edgington Road Bridge

Information and Findings From Ohio's Historic Bridge Inventory

Setting/Context

The bridge carries a 1 lane rural road over a stream in a rural area of active farms. It is posted for 6 tons.

Physical Description

The 1 span, 50'-long, wrought-iron, pin-connected, Pratt pony truss bridge has built-up compression members and eyebar tension members. Those at the end panels are connected with upturned ends through cast iron connecting pieces, a detail common to early WIBC metal truss bridges. The verticals are built up using the bulb or beaded T section that is also a hallmark of the company and was intended to make a stiffer member. The abutments are stone. The floorbeams are in kind replacements of the originals.

Integrity

Impacted rust.

Summary of Significance

The pin connected Pratt pony truss bridge dated stylistically to ca. 1880 and the Wrought Iron Bridge Co. and is historically and technologically significant as a complete example of the early pony truss design of the important fabricator. Another example built in 1874 (5630146) is also significant. It is one of 20 examples of the bridge type in Morrow County with the oldest extant example dating to 1874. It is also one of 13 very similar WIBC pony truss bridges in the state. It is know that Morrow County was buying this bridge design from WIBC in 1874.

Pratt trusses were undoubtedly the most popular truss design of the last quarter of the 19th century and continued to be built into the 20th century. The design, which initially was a combination of wood compression and iron tension members, was patented in 1844 by Thomas & Caleb Pratt. The great advantage of the Pratt over other designs was the relative ease of calculating the distribution of stresses. More significantly, it translated well into an all-metal design in lengths of less than 200'. Prior to about 1890, a variety of panel point connections (including bolts, cast-iron pieces, and pins like those seen on this bridge) and lower chord designs were in widespread use. Many of the connection details were proprietary and associated with individual builders or companies, and thus earlier examples are generally taken to be technologically significant in showing the evolution of the design. Post-1890 Pratt trusses show a progression toward less variation in their details such that by 1895 the design was quite formulaic with few significant differences between the designs of various builders. This marked the end of the pin-connected Pratt's technological evolution and, in fact, it was soon eclipsed in the highway bridge market by more rigid, rivet-connected truss designs, particularly the Warren design, but also the Pratt design as well. The transition to riveted field connections, which happened even earlier with railroads than highways, was in no small part due to concerns about stress reversals at the pins under heavier loads and improvements in pneumatic field riveting equipment in the early 1900s. In Ohio, there are 185 Pratt trusses dating from ca. 1874 to 1945 with at least 60 dating prior to 1900 (Phase 1A, 2008). The technologically significant unaltered examples of pin-connected Pratt trusses for the most part date prior to 1895 and have documented or attributed builders and dates of construction and/or significant connection or member details. Post-1895 examples are less technologically significant.

Justification

The bridge is one of over 150 extant pin-connected truss bridges dating from 1874 for pony trusses and 1876 for thru trusses. Twenty six predate 1888 and represent the era of experimentation that evolved into standardized designs by about 1888. This example has moderate significance because the genre and the fabricator are so well represented in Ohio.

Bridge Considered Historic By Survey: Yes